Although hyperthermia significantly increases the effectiveness of radiation therapy, large tumors with limited radiation tolerance often cannot be controlled. Appropriately selected and scheduled anticancer drugs should increase the efficacy of radiation plus hyperthermia. We will attempt to develop maximally effective combination therapies based on the following mechanistic hypotheses: 1. Certain anticancer drugs plus hyperthermia increase the DNA damage due to radiation in a more than additive fashion by causing more initial breaks, qualitatively different lesions and/or inhibiting repair; 2. The level of cells in vitro; 3. The level of tumors in vivo. The DNA work will test the effect of pH, level elution, DNA sequencing and footprinting. The in vitro cellular studies will examine the effect of pH level of oxygenation and temperature on drug cytotoxicity, drug levels, and on the interaction of the drugs with radiation killing. The in vivo tumor studies will use growth delay, tumor excision and Hoechst 33342 dye selected subpopulations to test the antitumor effects and cytotoxicity of these treatments. In addition, whole tumors, tumor subpopulations, skin, muscle and a serum will be studied to determine drug pharmacology at normal vs. elevated temperature. Since patients treated in hyperthermia clinics have predominantly soft tissue sarcomas, breast cancers and head and neck cancers, we will study the murine FSaIIC fibrosarcoma, the MCF-7 human breast cancer and the SCC-25 human head and neck squamous cell cancer lines in vitro and in vivo (the latter two as xenografts). The drugs to be tested are cisplatin (CDDP), adriamycin, bleomycin, mitomycin C, etanidazole and SR 4233. These drugs were chosen because: 1. Each interacts positively with both hyperthermia and radiation; 2. Each current agent (SR 423 is entering Phase I), except Mito C, can be used weekly with hyperthermia during a course of radiation; and 3. Each current agent is effective in one or more of the three main tumor types we treat in the clinic. Our ultimate purpose in these studies is to understand the mechanisms of interaction between anticancer drugs, hyperthermia and radiation from the level of DNA damage to the level of environmentally determined tumor cell subpopulations and to use this knowledge to develop maximally effective combination therapies for use in the clinic.